Someone can certainly double check me on this, but here is my best shot off the top of my head. (Great movie AND book by the way.)
1. Wesley
2. Inigo & Fezzik
3. The 6 fingered man
4. Prince Humperdinck
5. The Sicilian (who is evil and could probably be considered a villian but still provides help in the form of Inigo and Fezzik in the end) or Miracle Max (?)
6. The Dread Pirate Roberts
7. Buttercup
8. A peasant farmer with little relevance to the story.